For preparing a coffee beverage, usually a powder made of ground coffee beans is used. In order to brew up this coffee powder, in many cases use is made of a semi-automatic or automatic coffee machine, a so-called espresso machine, in which the coffee powder is brewed under pressure. Fully automatic espresso machines often have an integrated coffee grinder to grind the coffee beans just before the coffee powder is needed. Moreover, manually preparing a coffee beverage with the help of a filter receiving the coffee powder is well known.
In the case of a semi-automatic coffee machine, a certain amount of coffee powder is filled into a filter holder by means of a dosing mug. Then, the filter holder is inserted into the coffee machine whereby the coffee powder contained therein is compressed. Now, hot water is led under pressure through the filter holder containing the compressed coffee powder and the resulting coffee beverage is collected. Another variant for preparing a coffee beverage with the help of a semi-automatic coffee machine consists in that, instead of manually dosing a certain amount of loose coffee powder, a prepared, prepackaged single-portion of coffee powder is used. Such single-portions comprise a certain amount of industrially ground coffee powder, included in a package which can be of various design. For instance, single-portions of ground coffee are known which are received in small containers made of plastic foils, metal foils, filter paper or a combination of these materials.
The advantage of these pre-packaged single-portions of ground coffee may be seen in the fact that the desired amount of coffee powder is already measured off and ground with the help of professional coffee grinders exactly to the optimal grain size. A further essential advantage is that the coffee machine is subjected but to a slight contamination since the coffee powder does not come into direct contact with parts or elements of the coffee machine.
Disadvantageous is that the single-portions of ground coffee must be received in expensive packages since it is required that each single-portion of ground coffee must be hermetically sealed. Thus, a coffee beverage, after all, is substantially more expensive than a coffee beverage brewed with the help of conventional methods. Moreover, a fully automatic coffee machine is very difficult to design if it has to be operated with such single-portions of ground coffee, since particularly a reliably operating feeding mechanism for the single-portions is hard to realize with reasonable expenditure. Furthermore, the hermetically sealed single-portions of coffee powder must be opened prior to the brewing operation. On the other hand, if the single-portions of coffee powder are not hermetically sealed, there is a danger that atmospheric influences, particularly the oxygen and the humidity contained in the atmosphere, have a detrimental effect on the taste and the flavor of the ground coffee.